Hydraulic System: Service and Repair
Caution: Do not move the vehicle until a firm brake pedal is obtained. Air in the brake system can cause the loss of brakes with possible personal injury.
Caution: Use only Delco Supreme 11 (GM P/N 12377967) or equivalent DOT 3 brake fluid from a clean, sealed container. Do not use fluid from an open container that may be contaminated with water. Improper or contaminated fluid could result in damage to components, or loss of braking, with possible injury.
Caution: Do not overfill the brake fluid reservoir. Overfilling the brake fluid reservoir may cause the brake fluid to overflow onto the engine exhaust components during brake system service. The brake fluid is flammable and may cause a fire and persona/ injury if the brake fluid contacts the engine exhaust system components.
Notice: Refer to Brake Fluid Damage to Electrical Connections Notice in Service Precautions.
Notice: If any brake component is repaired or replaced such that air is allowed to enter the brake system, the entire bleeding procedure must be followed.
Notice: Prior to bleeding the brakes, the front and rear displacement cylinder pistons must be returned to the topmost position. The preferred method uses a Scan Tool to perform the rehoming procedure. If a Scan Tool is not available, the second procedure may be used, but it is extremely important that the procedure be followed exactly as outlined.
A bleeding operation is necessary in order to remove air when air is introduced into the hydraulic brake system.
Bleed the hydraulic system at all four brakes if air has been introduced through a low fluid level or by disconnecting brake pipes at the master cylinder. If a brake hose or brake pipe is disconnected at one wheel, bleed only that one wheel caliper. If brake pipes or hoses are disconnected at any fitting located between the master cylinder and the brakes, then only bleed the brake system served by the disconnected pipe or hose.
Pressure Flushing
^ Tools Required
- J 29532 Diaphragm Type Brake Bleeder
- J 35589 Compact Brake Bleeder Adapter
Important:
^ If evidence of contamination is present in the vehicle's brake fluid, flush the entire brake system following one of the following procedures.
^ Flush the system under the following conditions:
- If there is any doubt about the condition of the fluid in the system
- If the fluid that is used contains the slightest trace of mineral oil (engine oil, transmission fluid, etc.)
^ After flushing the entire brake system, replace all rubber components.
- Replace the following components. Refer to the appropriate replacement procedures.
- The brake hose assemblies
- The master cylinder rubber parts
- The brake caliper and wheel cylinder boots and seals
- The ABS modulator
- The proportioning valve
^ After replacing all rubber components, re-flush the entire brake system by performing one of the following procedures.
^ After performing the second flushing procedure, perform a complete system bleed. Refer to Hydraulic Brake System Bleeding.
Notice: Pressure Bleeding equipment can be used to perform the flush procedure. The pressure bleeding equipment used for flushing must be of the diaphragm type. It must a have a rubber diaphragm between the air supply and the brake fluid to prevent air, moisture, and other contaminants from entering the hydraulic system.
1. Clean the brake fluid reservoir cover and the surrounding area.
2. Remove the brake fluid reservoir cover.
Caution: Refer to Brake Fluid Irritant Caution in Service Precautions.
Notice: Refer to Brake Fluid Damage to Electrical Connections Notice in Service Precautions.
3. Remove any remaining brake fluid in the reservoir.
4. Refill the brake fluid reservoir (1). Use Delco Supreme No. II Hydraulic Brake Fluid (GM P/N 12377967) or equivalent DOT-3 motor vehicle brake fluid.
5. Replace all the rubber components listed under the flushing procedure.
6. Repeat the flushing procedure.
7. Inspect the brake fluid level in the reservoir (1). Fill the reservoir to the correct level if necessary.
8. Install the brake fluid reservoir cap.
9. Bleed the entire brake hydraulic system. Refer to Hydraulic Brake System Bleeding.
Manual Flushing
Caution: Refer to Brake Fluid Irritant Caution in Service Precautions.
Notice: Refer to Brake Fluid Damage to Electrical Connections Notice in Service Precautions.
1. Remove the battery tray.
2. Clean the brake fluid reservoir cover and the surrounding area.
3. Remove the brake fluid reservoir cover.
4. Remove any remaining brake fluid in the brake fluid reservoir.
5. Refill the brake fluid reservoir (1). Use Delco Supreme No. II Hydraulic Brake Fluid (GM P/N 12377967) or equivalent DOT-3 motor vehicle brake fluid.
6. Install the brake fluid reservoir cover.
Notice: Refer to Fastener Notice in Service Precautions.
7. Use the following procedure in order to flush the brake modulator:
7.1. Attach the bleeder hose to the rearward bleeder valve.
7.2. Submerge the opposite hose end in a clean container partially filled with clean brake fluid.
7.3. Slowly open the rearward bleeder valve.
7.4. Depress the brake pedal and hold the pedal until the fluid begins to flow.
7.5. Close the valve and release the brake pedal. Repeat the above steps until clean brake fluid flows or at least 118 ml (4 oz.) of fluid accumulates.
7.6. Repeat the procedure for the forward bleeder valve until clean brake fluid flows or at least 118 ml (4 oz.) of fluid accumulates.
^ Tighten the ABS brake modulator bleeder valves to 9 Nm (80 inch lbs.).
8. Inspect the brake fluid level and add brake fluid if necessary.
9. Raise the vehicle. Refer to Vehicle Lifting.
10. Flush the brake system to the wheel brakes in the following sequence.
^ Right rear brake
^ Left front brake
^ Left rear brake
^ Right front brake
11. Use the following procedure in order to flush the brake system to the wheels:
11.1. Attach the bleeder hose (3) to the bleeder valve.
11.2. Submerge the opposite hose end in a clean container partially (2) filled with clean brake fluid.
11.3. Slowly open the bleeder valve.
11.4. Depress the brake pedal and hold the pedal until the fluid begins to flow.
11.5. Close the bleeder valve and release the brake pedal. Repeat the above steps until clean brake fluid flows or at least 235 ml (8 oz.) of fluid accumulates.
11.6. Inspect the brake fluid level and add brake fluid if necessary. Do not let the brake fluid reservoir go empty.
^ Tighten the front caliper bleeder valves to 13 Nm (115 inch lbs.).
^ Tighten rear caliper bleeder valves to 7 Nm (62 inch lbs.).
^ Tighten the rear wheel cylinder bleeder valves to 7 Nm (62 inch lbs.).
12. Lower the vehicle.
13. Replace all of the following rubber components:
^ The brake hose assemblies
^ The master cylinder rubber parts
^ The brake caliper and wheel cylinder boots and seals
^ The ABS modulator
^ The proportioning valve
14. Repeat the manual flushing procedure.
15. Inspect the brake fluid level in the reservoir. Fill the reservoir to the correct level if necessary.
16. Replace the brake fluid reservoir cap.
17. Bleed the entire brake hydraulic system. Refer to Hydraulic Brake System Bleeding.
18. Install the battery tray.